Just thought I'd throw in my two-pennorth here. Been having the same problem over the last couple of months with Firefox 55.0.3 (64-bit) running on Windows 10 Pro. It has been so bad that I've often waited for up to 5 minutes while the 'Performing TLS handshake with .......' message displays.Yesterday I installed Chrome. Attempted to connect to a music forum using Firefox that I've had the TLS problem with and as usual got the message. Immediately started Chrome and attempted to connect with the same forum. No problem. Read a couple of comments, replied to one and logged out. Meanwhile, Firefox was still waiting with the TLS message.....A few seconds after I had completed the exercise using Chrome, Firefox decided to connect me.....I have previously tried all the solutions suggested here, emptying the cache, going to No Proxy, turning off IPv6 etc. but nothing had worked in Firefox.I'll add that I am running both Avast Anti-virus and Malwarebytes. Turning off these had no effect on the Firefox TLS problem. Both were running when I successfully connected using Chrome.I am reluctant to discard Firefox as previously I have found it to be fast and reliable, but something has happened the last few months to dent my confidence....Just tried it again today to the same site, and it took 85 seconds to connect to the forum page with Firefox. With Chrome, the connection was almost instantaneous..................